1. Field of the Invention
The present invention relates to an optical frequency measurement apparatus and an optical frequency measurement method. More particularly, the present invention relates to an optical frequency measurement apparatus and an optical frequency measurement method for measuring optical frequency of measured input light.
2. Related Art
Wavelength-division multiplexing communication (WDM) has been developed in order to significantly increase transmission capacity of fiber optic communications. In recent years, multiple-wavelength transmission exceeding 100 channels has been realized, and further high-density multiple-wavelength transmission (DWDM) having an extremely narrow channel spacing of 50 GHz has been realized.
Now, since a related patent document is not recognized, the description is omitted.
In a light wavelength-division multiplexing communication system, it is necessary to accurately monitor optical frequency of each channel to maintain and manage the optical frequency, in order to suppress a cross talk between the channels. For example, when each channel having a channel spacing of 50 GHz performs communication of 40 G bits per second, an allowable error for optical frequency of each channel is around 2.5 GHz, and an allowable error for optical frequency of 1.5 μm band (C band) is around 10-5 to 10-6. Then, a test and a correction for a light wavelength-division multiplexing communication system and the parts further request high measurement accuracy.